CVE-2026-64581

CVE CVE-2026-64581EUVD EUVD-2026-53275Published 2026-08-05T08:09:35.000ZLast changed 2026-08-08T15:13:18.000ZCVSS 7.8

What the advisory describes

In the Linux kernel, the following vulnerability has been resolved: xfrm: fix sk_dst_cache double-free in xfrm_user_policy() xfrm_user_policy() clears the socket dst cache with __sk_dst_reset(), i.e. the non-atomic __sk_dst_set(sk, NULL): it reads sk_dst_cache with rcu_dereference_protected(), stores NULL and dst_release()s the old dst. That is only safe if no other thread modifies sk_dst_cache concurrently. For a connected UDP socket that does not hold: the transmit fast path (udp_sendmsg -> sk_dst_check -> sk_dst_reset) resets the cache locklessly with an atomic xchg(). A per-socket policy change racing a send can make both sides observe the same old dst and each dst_release() it, dropping the socket's single reference twice and freeing the xfrm_dst bundle while it is still referenced: BUG: KASAN: slab-use-after-free in dst_release Write of size 4 at addr ffff88801897b6c0 by task exploit/155 Call Trace: ... dst_release (... ./include/linux/rcuref.h:109) xfrm_user_policy (./include/net/sock.h:2239 ./include/net/sock.h:2256 net/xfrm/xfrm_state.c:3053) do_ip_setsockopt (net/ipv4/ip_sockglue.c:1347) ip_setsockopt (net/ipv4/ip_sockglue.c:1417) do_sock_setsockopt (net/socket.c:2368) __sys_setsockopt (net/socket.c:2393) __x64_sys_setsockopt (net/socket.c:2396) do_syscall_64 (arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Reachable by an unprivileged user via a user+network namespace. Use the atomic sk_dst_reset() so the cache is cleared and released with a single xchg(): whichever side wins releases the dst once, the other sees NULL and does nothing. Behaviour is otherwise unchanged.

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

• Linux — Linux 4.4.163 <4.5; 4.9.89 <4.10; 4.1.52 <4.2; 5eef9b51114fcc65651d671add52f267f91b9451; 9e9fe58a92a46c6d154d2901735bf230d91b8507; 4.4.123 <4.5; c9e82cb34c3c2ee895af01bc899c6ed0bc6eb04a; 3.18.101 <3.19; patch: 0; 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 <96b678d08268b5f5c6fc99d4289d9b7e334fc683; 3.16.52 <3.17; adc1ec6cdc20d430aa01b86497220709b9149466; patch: 7.1.6; 4.14; patch: 7.2-rc4; 72f157be2f81910ae759bfe2e5c2256fc4625645; b54033eb1cfd77aba471269ddd804ed8d3e35dea; 2b06cdf3e688b98fcc9945873b5d42792bd4eee0 <c283e9ada7fcb7dd4b10592623086b2e6d2f9925

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

• Linux — Linux

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